How to change font-size in site title in Neve?
⏪ Before

⏩ After
For changing the font-size of the site title and tagline, add the following code to the Additional CSS editor within the Customizer.
p.site-title {
font-size: 25px;
}
.site-logo small {
font-size: 20px;
}

Feel free to change the values as you want. In case this doesn't work as expected, we are here to help you.
📝 Note: In the PRO version of Neve, this feature is available within the Customizer, by navigating to Appearance > Customize > Header, click on the Logo & Site Identity component, and increasing Logo max width.